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Mitchell L Wise - One of the best experts on this subject based on the ideXlab platform.
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tissue distribution of Avenanthramides and gene expression of hydroxycinnamoyl coa hydroxyanthranilate n hydroxycinnamoyl transferase hht in benzothiadiazole treated oat avena sativa 1
Canadian Journal of Plant Science, 2017Co-Authors: Mitchell L WiseAbstract:Oats produce a group of natural products termed Avenanthramides. These compounds are produced in both the vegetative tissue and the grain. They are produced in leaf tissue in response to crown rust...
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in vivo suppression of atherosclerosis by dietary oats Avenanthramides
The FASEB Journal, 2016Co-Authors: Michael G Thomas, Mitchell L Wise, William F Collins, Sharon Kim, Mohsen MeydaniAbstract:The consumption of oatmeal and oat bran has been shown to reduce total and low density lipoprotein (LDL) cholesterol levels in plasma, which are major risk factors for coronary heart disease (CHD)....
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in vitro total antioxidant capacity and anti inflammatory activity of three common oat derived Avenanthramides
Food Chemistry, 2014Co-Authors: Jun Yang, Mitchell L Wise, Yifang ChuAbstract:To better understand mechanisms underlying the health benefits of oats, the free radical scavenging capacities of oat Avenanthramides 2c, 2f, and 2p and their ability to inhibit NF-κB activation were evaluated. The antioxidant capacities of 2c, 2f, and 2p against peroxyl radicals, hydroxyl radicals, superoxide anion, singlet oxygen, and peroxynitrite were determined by using ORAC, HORAC, SORAC, SOAC, and NORAC assays, respectively. The total antioxidant capacity of 2c was approximately 1.5-fold those of 2f and 2p. Total antioxidant capacity was primarily attributable to SORAC and ORAC for 2c (>77%, p<0.05), and to ORAC and SOAC for 2f. ORAC accounted for approximately 32% of total antioxidant capacity in 2p. EC50 values for inhibiting TNF-α-induced NF-κB activation in C2C12 cells were 64.3, 29.3, and 9.10 μM for 2c, 2f, and 2p, respectively. Differences in antioxidant capacities and ability to inhibit NF-κB among the Avenanthramides could be ascribed to structural variations.
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in vitro antioxidant capacity and anti inflammatory activity of seven common oats
Food Chemistry, 2013Co-Authors: Yifang Chu, Mitchell L Wise, Apeksha A Gulvady, Tony Chang, David F Kendra, Janwillem B Van Klinken, Yuhui Shi, Marianne OsheaAbstract:Abstract Oats are gaining increasing scientific and public interest for their purported antioxidant-associated health benefits. Most reported studies focused on specific oat extracts or particular oat components, such as β-glucans, tocols (vitamin E), or Avenanthramides. Studies on whole oats with respect to antioxidant and anti-inflammatory activities are still lacking. Here the antioxidant and anti-inflammatory activities from whole oat groats of seven common varieties were evaluated. All oat varieties had very similar oxygen radical absorption capacity compared with other whole grains. In an anti-inflammatory assay, oat variety CDC Dancer inhibited tumor necrosis factor-α induced nuclear factor-kappa B activation by 27.5% at 2 mg/ml, whereas variety Deiter showed 13.7% inhibition at a comparable dose. Avenanthramide levels did not correlate with the observed antioxidant and anti-inflammatory activities. Further investigations are needed to pinpoint the specific antioxidant and anti-inflammatory compounds, and potential synergistic and/or matrix effects that may help explain the mechanisms of oat’s anti-inflammatory actions.
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effect of chemical systemic acquired resistance elicitors on avenanthramide biosynthesis in oat avena sativa
Journal of Agricultural and Food Chemistry, 2011Co-Authors: Mitchell L WiseAbstract:Oats produce a group of phenolic antioxidants termed Avenanthramides. These metabolites are, among food crops, unique to oats and have shown, in experimental systems, certain desirable nutritional characteristics such as inhibiting atherosclerotic plaque formation and reducing inflammation. Avenanthramides occur in both the leaves and grain of oat. In the leaves they are expressed as phytoalexins in response to crown rust (Puccina coronata) infection. The experiments reported here demonstrate that avenanthramide levels in vegetative tissue can be enhanced by treatment with benzothiadiazole (BTH), an agrochemical formulated to elicit systemic acquired resistance (SAR). The response to BTH was dramatically stronger than those produced with salicylic acid treatment. The roots of BTH treated plants also showed a smaller but distinct increase in Avenanthramides. The dynamics of the root avenanthramide increase was substantially slower than that observed in the leaves, suggesting that Avenanthramides might be t...
Lena H Dimberg - One of the best experts on this subject based on the ideXlab platform.
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in vitro antioxidant activity and antigenotoxic effects of Avenanthramides and related compounds
Journal of Agricultural and Food Chemistry, 2009Co-Authors: Alison M Leemanion, Lena H Dimberg, Kerstin Sunnerheim, R K Price, James J Strain, Robert W WelchAbstract:Avenanthramides are substituted N-cinnamoylanthranilic acids, with hydroxycinnamic acid and anthranilic acid moieties. These alkaloid phenols, which are unique to oats, may confer health benefits via antioxidant or other mechanisms. Synthetic Avenanthramides, hydroxycinnamic acids, Tranilast, and ascorbic acid were evaluated for antioxidant activity using two assays, DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (ferric reducing antioxidant potential), and for antigenotoxicity using the Comet assay with stressed human adenocarcinoma colon cells. Of all the compounds tested, N-(3',4'-dihydroxy-(E)-cinnamoyl)-5-hydroxyanthranilic acid (2c), an abundant oat avenanthramide, generally had the highest activity in all three assays. The drug Tranilast showed antigenotoxic effects, but not antioxidant activity, suggesting that antigenotoxicity is not dependent on antioxidant effects. Overall, results show that Avenanthramides exert antioxidant and antigenotoxic activities that are comparable to those of ascorbic acid and which have the potential to exert beneficial physiological effects.
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phenols in spikelets and leaves of field grown oats avena sativa with different inherent resistance to crown rust puccinia coronata f sp avenae
Journal of the Science of Food and Agriculture, 2009Co-Authors: Lena H Dimberg, David M PetersonAbstract:BACKGROUND: Avenanthramides, health-beneficial phenols in oats, are produced in response to incompatible races of the crown rust fungus, Puccinia coronata, in seedlings of greenhouse-grown oats. This study aimed to elucidate whether Avenanthramides and/or other phenolic compounds, together with the activities of phenylalanine ammonia lyase (PAL), phenoloxidase (PO) and the avenanthramide biosynthetic enzyme hydroxycinnamoyl-CoA:hydroxyanthranilate-N-hydroxycinnamoyl transferase (HHT), are associated with crown rust infection in mature field-grown oats. Nine oat (Avena sativa L.) genotypes with wide variation in crown rust resistance were exposed to naturally occurring fungal spores during the growth period. RESULTS: In the spikelets Avenanthramides as well as HHT activities were more abundant in the crown rust resistant genotypes, whereas p-coumaric and caffeic acids were more abundant in the susceptible ones. In the leaves Avenanthramides were not associated with resistance. Instead two unknown compounds correlated negatively with the rust score. Phenols released by alkaline hydrolysis and PAL and PO activities were not related to rust infection, either in spikelets or in the leaves. CONCLUSION: Because grains of crown rust-resistant oat genotypes seemed to have higher endogenous levels of health-promoting Avenanthramides, use of resistant oats may contribute to a food raw material with health-beneficial effects. Copyright © 2009 Society of Chemical Industry
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radical scavenging and antioxidant activity of Avenanthramides
Food Chemistry, 2009Co-Authors: Amelie Fagerlund, Kerstin Sunnerheim, Lena H DimbergAbstract:Avenanthramides are amides of cinnamoyl-anthranilic acids and, among cereals, are exclusively found in oats. This study investigated the structure-antioxidant activities of 15 Avenanthramides with ...
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avenanthramide content and related enzyme activities in oats as affected by steeping and germination
Journal of Cereal Science, 2008Co-Authors: Maria Skoglund, David M Peterson, Roger Andersson, Janicka Nilsson, Lena H DimbergAbstract:Abstract Samples from three different oat ( Avena sativa L.) cultivars, Vista, Gem and Dane were steeped and germinated in a pilot plant malting system. The content of Avenanthramides, antioxidant compounds unique to oats, and some unknown compounds as well as the activities of the avenanthramide-synthesising enzyme hydroxycinnamoyl-CoA:hydroxyanthranilate N -hydroxycinnamoyl transferase (HHT) and the avenanthramide-oxidizing enzyme phenoloxidase (PO) were measured. An increase in avenanthramide content of germinated seeds, as compared to raw grains, was observed for Dane (125%, p p = 0.007). The HHT activity increased 62% ( p = 0.014) in Dane, whereas no change was detected in Vista and Gem. The PO activity decreased slightly during the germination process for Gem ( p p = 0.005). Many of the unknown compounds increased significantly during germination in all three cultivars, and one of them was identified to be the avenanthramide N -(4′-hydroxy-3′-methoxy-( E )-cinnamoyl)-5-hydroxy-4-methoxyanthranilic acid. This study indicates that a highly controlled steeping and germination process can be a valuable method to increase the content of endogenous Avenanthramides in oats.
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selective and sensitive lc ms determination of Avenanthramides in oats
Chromatographia, 2006Co-Authors: Jelena Jastrebova, Janicka Nilsson, M Skoglund, Lena H DimbergAbstract:A new liquid chromatographic – mass spectrometric (LC-MS) method suitable for the determination of Avenanthramides in oats has been developed. The Avenanthramides were detected using positive ion electrospray with selective ion monitoring of protonated ions [M+H]+. The separation of Avenanthramides was achieved on Genesis C18 column by using acetonitrile – aqueous formic acid as mobile phase and gradient elution. The effects of buffer nature and concentration on separation, peak shape and intensity of mass spectrometric signal were investigated. The detection limits ranged between 10 and 30 ng mL−1 for standard solutions when using 1 μL injection. The developed LC-MS method was found to be superior over commonly used liquid chromatographic methods with UV detection in terms of selectivity and sensitivity. The applicability of the method to real samples (oat groats) was demonstrated.
David M Peterson - One of the best experts on this subject based on the ideXlab platform.
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phenols in spikelets and leaves of field grown oats avena sativa with different inherent resistance to crown rust puccinia coronata f sp avenae
Journal of the Science of Food and Agriculture, 2009Co-Authors: Lena H Dimberg, David M PetersonAbstract:BACKGROUND: Avenanthramides, health-beneficial phenols in oats, are produced in response to incompatible races of the crown rust fungus, Puccinia coronata, in seedlings of greenhouse-grown oats. This study aimed to elucidate whether Avenanthramides and/or other phenolic compounds, together with the activities of phenylalanine ammonia lyase (PAL), phenoloxidase (PO) and the avenanthramide biosynthetic enzyme hydroxycinnamoyl-CoA:hydroxyanthranilate-N-hydroxycinnamoyl transferase (HHT), are associated with crown rust infection in mature field-grown oats. Nine oat (Avena sativa L.) genotypes with wide variation in crown rust resistance were exposed to naturally occurring fungal spores during the growth period. RESULTS: In the spikelets Avenanthramides as well as HHT activities were more abundant in the crown rust resistant genotypes, whereas p-coumaric and caffeic acids were more abundant in the susceptible ones. In the leaves Avenanthramides were not associated with resistance. Instead two unknown compounds correlated negatively with the rust score. Phenols released by alkaline hydrolysis and PAL and PO activities were not related to rust infection, either in spikelets or in the leaves. CONCLUSION: Because grains of crown rust-resistant oat genotypes seemed to have higher endogenous levels of health-promoting Avenanthramides, use of resistant oats may contribute to a food raw material with health-beneficial effects. Copyright © 2009 Society of Chemical Industry
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avenanthramide content and related enzyme activities in oats as affected by steeping and germination
Journal of Cereal Science, 2008Co-Authors: Maria Skoglund, David M Peterson, Roger Andersson, Janicka Nilsson, Lena H DimbergAbstract:Abstract Samples from three different oat ( Avena sativa L.) cultivars, Vista, Gem and Dane were steeped and germinated in a pilot plant malting system. The content of Avenanthramides, antioxidant compounds unique to oats, and some unknown compounds as well as the activities of the avenanthramide-synthesising enzyme hydroxycinnamoyl-CoA:hydroxyanthranilate N -hydroxycinnamoyl transferase (HHT) and the avenanthramide-oxidizing enzyme phenoloxidase (PO) were measured. An increase in avenanthramide content of germinated seeds, as compared to raw grains, was observed for Dane (125%, p p = 0.007). The HHT activity increased 62% ( p = 0.014) in Dane, whereas no change was detected in Vista and Gem. The PO activity decreased slightly during the germination process for Gem ( p p = 0.005). Many of the unknown compounds increased significantly during germination in all three cultivars, and one of them was identified to be the avenanthramide N -(4′-hydroxy-3′-methoxy-( E )-cinnamoyl)-5-hydroxy-4-methoxyanthranilic acid. This study indicates that a highly controlled steeping and germination process can be a valuable method to increase the content of endogenous Avenanthramides in oats.
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mechanism by which avenanthramide c a polyphenol of oats blocks cell cycle progression in vascular smooth muscle cells
Free Radical Biology and Medicine, 2006Co-Authors: Lin Nie, Mitchell L Wise, David M Peterson, Mohsen MeydaniAbstract:Abstract Previously, we reported that avenanthramide-c (Avn-c), one of the major Avenanthramides, polyphenols of oats, inhibited the serum-induced proliferation of vascular smooth muscle cells (SMC), which is an important process in the initiation and development of atherosclerosis. In the present study, we further investigated its cell cycle inhibitory mechanism. Rat embryonic aortic smooth muscle cell line A10 was used in this study. Flow cytometry analysis revealed that treatment of A10 cells with 80 μM Avn-c arrested the cell cycle in G1 phase as indicated by an increase in the number of cells in G1 phase and a decrease in the number of cells in S phase. This cell cycle arrest was associated with a decrease in the phosphorylation of retinoblastoma protein (pRb), whose hyperphosphorylation is a hallmark of the G1 to S transition in the cell cycle. The inhibition of pRb phosphorylation with Avn-c was accompanied by a decrease in cyclin D1 expression and an increase in cyclin-dependent kinase inhibitor p21cip1 expression, without significant changes in p27kip1 expression. Furthermore, Avn-c treatment increased the expression level and stability of p53 protein, which could account for the increase of p21cip1 expression. Our results demonstrate for the first time that Avn-c, which is a unique polyphenol found in oats, arrests SMC proliferation at G1 phase by upregulating the p53-p21cip1 pathway and inhibiting pRB phosphorylation. This inhibitory effect of Avn-c on SMC proliferation is an additional indication for the potential health benefit of oat consumption in the prevention of coronary heart disease beyond its known effect through lowering blood cholesterol.
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avenanthramide a polyphenol from oats inhibits vascular smooth muscle cell proliferation and enhances nitric oxide production
Atherosclerosis, 2006Co-Authors: Lin Nie, Mitchell L Wise, David M Peterson, Mohsen MeydaniAbstract:The proliferation of vascular smooth muscle cells (SMC) and impaired nitric oxide (NO) production are both crucial pathophysiological processes in the initiation and development of atherosclerosis. Epidemiological data have indicated that diets rich in whole grain foods are associated with a reduced risk of developing atherosclerosis. Avenanthramides are polyphenols found exclusively in oats (Avena sativa L.). The present study was conducted to examine the effect of synthetically prepared avenanthramide-2c on the proliferation of SMC and NO production by SMC and human aortic endothelial cells (HAEC). Avenanthramide-2c significantly inhibited serum-induced SMC proliferation. At a concentration of 120 microM, avenanthramide-2c inhibited more than 50% of SMC proliferation, as measured by [3H] thymidine incorporation, and increased the doubling time of rat SMC line (A10) from 28 to 48 h. Treatment of human SMC with 40, 80, and 120 microM avenanthramide-2c inhibited cell number increase by 41, 62, and 73%, respectively. In addition, avenanthramide-2c treatment significantly and dose-dependently increased NO production in both SMC and HAEC. At a concentration of 120 microM, avenanthramide-2c increased NO production by three-fold in SMC, and by nine-fold in HAEC. These increases were in parallel with the up-regulation of mRNA expression for endothelial NO synthase (eNOS) in both vascular SMC and HAEC. These results suggest that the Avenanthramides of oats may contribute to the prevention of atherosclerosis through inhibition of SMC proliferation and increasing NO production.
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oat Avenanthramides exhibit antioxidant activities in vitro
Food Chemistry, 2002Co-Authors: David M Peterson, Martha J Hahn, Cheryld L EmmonsAbstract:Abstract Avenanthramides are a group of alkaloids that consist of an anthranilic acid derivative linked to a hydroxycinnamic acid derivative by a pseudo peptide bond, which are constituents of oat ( Avena sativa L.) grain. The three most abundant Avenanthramides, N -(4′-hydroxy-3′-methoxycinnamoyl)-5-hydroxyanthranilic acid (Bf), N -(4′-hydroxycinnamoyl)-5-hydroxyanthranilic acid (Bp), and N -(3′,4′-dihydroxycinnamoyl)-5-hydroxyanthranilic acid (Bc), were synthesized and purified. These were tested for antioxidant activity using two in vitro systems: inhibition of β-carotene bleaching and reaction with the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). Each avenanthramide displayed antioxidant activity in both systems. Bc had greater activity than Bp and Bf. Bc was nearly as active as the standard synthetic antioxidant, butylated hydroxytoluene (BHT) in the β-carotene system. In the DPPH system, Bc and Bf were more active than 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox®). The relative activities of the Avenanthramides corresponded to those determined for their component hydroxycinnamic acid moieties using an aqueous DPPH system or in a lipophilic system that measured the autoxidation of methyl linoleate.
Mohsen Meydani - One of the best experts on this subject based on the ideXlab platform.
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in vivo suppression of atherosclerosis by dietary oats Avenanthramides
The FASEB Journal, 2016Co-Authors: Michael G Thomas, Mitchell L Wise, William F Collins, Sharon Kim, Mohsen MeydaniAbstract:The consumption of oatmeal and oat bran has been shown to reduce total and low density lipoprotein (LDL) cholesterol levels in plasma, which are major risk factors for coronary heart disease (CHD)....
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potential health benefits of Avenanthramides of oats
Nutrition Reviews, 2009Co-Authors: Mohsen MeydaniAbstract:Oats are known to be a healthy food for the heart due mainly to their high β-glucan content. In addition, they contain more than 20 unique polyphenols, Avenanthramides, which have shown strong antioxidant activity in vitro and in vivo. The polyphenols of oats have also recently been shown to exhibit anti-inflammatory, antiproliferative, and anti-itching activity, which may provide additional protection against coronary heart disease, colon cancer, and skin irritation.
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mechanism by which avenanthramide c a polyphenol of oats blocks cell cycle progression in vascular smooth muscle cells
Free Radical Biology and Medicine, 2006Co-Authors: Lin Nie, Mitchell L Wise, David M Peterson, Mohsen MeydaniAbstract:Abstract Previously, we reported that avenanthramide-c (Avn-c), one of the major Avenanthramides, polyphenols of oats, inhibited the serum-induced proliferation of vascular smooth muscle cells (SMC), which is an important process in the initiation and development of atherosclerosis. In the present study, we further investigated its cell cycle inhibitory mechanism. Rat embryonic aortic smooth muscle cell line A10 was used in this study. Flow cytometry analysis revealed that treatment of A10 cells with 80 μM Avn-c arrested the cell cycle in G1 phase as indicated by an increase in the number of cells in G1 phase and a decrease in the number of cells in S phase. This cell cycle arrest was associated with a decrease in the phosphorylation of retinoblastoma protein (pRb), whose hyperphosphorylation is a hallmark of the G1 to S transition in the cell cycle. The inhibition of pRb phosphorylation with Avn-c was accompanied by a decrease in cyclin D1 expression and an increase in cyclin-dependent kinase inhibitor p21cip1 expression, without significant changes in p27kip1 expression. Furthermore, Avn-c treatment increased the expression level and stability of p53 protein, which could account for the increase of p21cip1 expression. Our results demonstrate for the first time that Avn-c, which is a unique polyphenol found in oats, arrests SMC proliferation at G1 phase by upregulating the p53-p21cip1 pathway and inhibiting pRB phosphorylation. This inhibitory effect of Avn-c on SMC proliferation is an additional indication for the potential health benefit of oat consumption in the prevention of coronary heart disease beyond its known effect through lowering blood cholesterol.
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avenanthramide a polyphenol from oats inhibits vascular smooth muscle cell proliferation and enhances nitric oxide production
Atherosclerosis, 2006Co-Authors: Lin Nie, Mitchell L Wise, David M Peterson, Mohsen MeydaniAbstract:The proliferation of vascular smooth muscle cells (SMC) and impaired nitric oxide (NO) production are both crucial pathophysiological processes in the initiation and development of atherosclerosis. Epidemiological data have indicated that diets rich in whole grain foods are associated with a reduced risk of developing atherosclerosis. Avenanthramides are polyphenols found exclusively in oats (Avena sativa L.). The present study was conducted to examine the effect of synthetically prepared avenanthramide-2c on the proliferation of SMC and NO production by SMC and human aortic endothelial cells (HAEC). Avenanthramide-2c significantly inhibited serum-induced SMC proliferation. At a concentration of 120 microM, avenanthramide-2c inhibited more than 50% of SMC proliferation, as measured by [3H] thymidine incorporation, and increased the doubling time of rat SMC line (A10) from 28 to 48 h. Treatment of human SMC with 40, 80, and 120 microM avenanthramide-2c inhibited cell number increase by 41, 62, and 73%, respectively. In addition, avenanthramide-2c treatment significantly and dose-dependently increased NO production in both SMC and HAEC. At a concentration of 120 microM, avenanthramide-2c increased NO production by three-fold in SMC, and by nine-fold in HAEC. These increases were in parallel with the up-regulation of mRNA expression for endothelial NO synthase (eNOS) in both vascular SMC and HAEC. These results suggest that the Avenanthramides of oats may contribute to the prevention of atherosclerosis through inhibition of SMC proliferation and increasing NO production.
Atsushi Ishihara - One of the best experts on this subject based on the ideXlab platform.
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New series of Avenanthramides in oat seed
2014Co-Authors: Atsushi Ishihara, Kana Kojima, Takeshi Fujita, Yuya Yamamoto, Hiromitsu NakajimaAbstract:Avenanthramides are characteristic constituents of oat seeds. We analyzed the methanol extract of oat seeds by HPLC and detected three compounds 1, 2, and 3 eluted at retention times similar to Avenanthramides. The three compounds were purified by column chromatography and HPLC. Spectroscopic analyses of 1, 2, and 3 suggested that they are amides of 4,5-dihydroxyanthranilic acid with caffeic, p-coumaric, and ferulic acids, respectively. Their identities were confirmed by comparing spectra and chromatographic behavior with compounds synthesized from 4,5-dihydroxyanthranilic acid and N-hyrdroxysuccinimide esters of hydroxycinnamic acids. LC-MS/MS analysis with multiple reaction monitoring showed that the amounts of 1, 2, and 3 were 16.5–26.9% of corresponding avenanthamides with 5-hydroxyanthranilic acid. Compounds 1, 2, and 3 showed stronger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity than the corresponding Avenanthramides with 5-hydroxyanthranilic acid, indicating the involvement of 4,5-dihydroxyanthranilic acid moiety in the scavenging of DPPH radicals.
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in situ localization of avenanthramide a and its biosynthetic enzyme in oat leaves infected with the crown rust fungus puccinia coronata f sp avenae
Physiological and Molecular Plant Pathology, 2011Co-Authors: Kohhei Uchihashi, Atsushi Ishihara, Hitoshi Nakayashiki, Kaoru Okamura, Yukio Tosa, Pyoyun Park, Shigeyuki MayamaAbstract:We determined the temporal and spatial localization of the phytoalexin avenanthramide A, and its biosynthetic enzyme, hydroxycinnamoyl-CoA:hydroxyanthranilate N-hydroxy-cinnamoyltransferase (AsHHT) in oat leaves infected with the crown rust fungus. Accumulation of avenanthramide A and AsHHT was first observed predominantly in hypersensitive response (HR) cells at 36 h post inoculation (hpi), and later in adjacent cells at 48 hpi. At 120 hpi, avenanthramide A was detected in a wider area of infected tissues, but AsHHT-positive signals were only observed in the HR and adjacent cells, suggesting that avenanthramide A was synthesized around the HR cells, and then transported to other parts of the infected tissues in a center-to-periphery manner.
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new dimeric compounds of avenanthramide phytoalexin in oats
Journal of Organic Chemistry, 2007Co-Authors: Yozo Okazaki, Atsushi Ishihara, Takaaki Nishioka, Akihiro Ishizuka, Hajime IwamuraAbstract:Avenanthramide B is an oat phytoalexin produced in response to pathogen attack and elicitation. We found the formation of new dimers (1−5) of avenanthramide B in elicited oat leaves. The dimers were synthesized by a reaction of peroxidase and avenanthramide B in the presence of hydrogen peroxide. The structures of 1−5 were determined by spectroscopic analyses, chemical derivatization, and 15N labeling. Compound 1 was a dehydrodimer of avenanthramide B with a bisbutane lactam skeleton, while 2−4 were monohydrated dehydrodimers with butane lactam structures. Compound 5 was also a monohydrated dehydrodimer but with a tetrahydrofuran structure. All the compounds were classified into lignanamides that were formed by an 8‘-8‘ coupling reaction between two avenanthramide B units.
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metabolism of avenanthramide phytoalexins in oats
Plant Journal, 2004Co-Authors: Yozo Okazaki, Hisashi Miyagawa, Atsushi Ishihara, Tetsuya Matsukawa, Taishi Isobe, Yoichi Iwata, Fumio Matsuda, Takaaki Nishioka, Hajime IwamuraAbstract:Oat leaves produce phytoalexins, Avenanthramides, in response to infection by pathogens or treatment with elicitors. The metabolism of Avenanthramides was investigated using low molecular weight, partially deacetylated chitin as an elicitor. When oat leaf segments are floated on the elicitor solution, Avenanthramides accumulate in the solution. The transfer of elicited oat leaves to solutions containing stable-isotope-labeled Avenanthramides resulted in a rapid decrease in the labeled Avenanthramides, suggesting the metabolism of Avenanthramides. The rate of decrease was enhanced by elicitor treatment, and was dependent on the species of Avenanthramides, with avenanthramide B decreasing most rapidly. The rates of biosynthesis and metabolism of Avenanthramides A and B were measured using a model of isotope-labeling dynamics. Avenanthramide B was found to be more actively biosynthesized and metabolized than avenanthramide A. Radiolabeled avenanthramide B was incorporated into the cell wall fraction and 99% of incorporated activity was released by alkaline treatment. Gel filtration indicated that high-molecular-weight compounds derived from avenanthramide B were released by alkaline treatment. The decrease in stable-isotope-labeled Avenanthramides was suppressed by catalase, salicylhydroxamic acid, and sodium ascorbate, suggesting the involvement of peroxidase in the metabolism. Consistent with this, peroxidase activity that accepts avenanthramide B as a substrate was induced in apoplastic fractions by elicitor treatment. The appearance of multiple basic isoperoxidases was observed by activity staining with 3-amino-9-ethylcarbazole coupled with isoelectric focusing of proteins from elicitor-treated leaves. These findings suggest that accumulated Avenanthramides are further metabolized in apoplasts in oat leaves by inducible isoperoxidases.
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levels of Avenanthramides and activity of hydroxycinnamoyl coa hydroxyanthranilate n hydroxycinnamoyl transferase hht in steeped or germinated oat samples
Cereal Chemistry, 2003Co-Authors: Susanne Bryngelsson, Atsushi Ishihara, Lena H DimbergAbstract:ABSTRACT Concentrations of Avenanthramides and activity of the biosynthetic enzyme hydroxycinnamoyl-CoA:hydroxyanthranilate N-hydroxycinnamoyl transferase (HHT) were analyzed in dry or, steeped nonmilled or milled, non-heat-treated (raw) or heat-treated oat samples (Avena sativa L.). Increased avenanthramide concentrations were found when intact raw groats were steeped. The increase was time- and temperaturedependent and maximal after 10 hr of steeping at 20°C. Continuous germination in air, after steeping, only contributed to a further increase in Avenanthramides when steeping times were shorter than 10 hr. Concentrations of Avenanthramides and HHT activity were positively correlated during steeping of intact groats at 8 and 20°C. The increase in Avenanthramides was suggested to be due to de novo synthesis and a whole grain structure seemed to be required as no increase was found when groats were milled before steeping. Avenanthramide levels also increased when heat-treated samples, lacking HHT activity,...
